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When Is a Mentally Disordered Person Dangerous?

The relationship between violence and mental illness is complex.

Key points

  • Individuals with a non-paranoid form of mental illness are not likely to be dangerous.
  • Obtrusive or inappropriate behavior is understandably concerning to others, but does not necessarily augur violence.
  • The mixture of mental illness and substance abuse is potentially dangerous.

How do you know if a seemingly unstable neighbor is dangerous, or if that strange distant relative who comes to visit is someone to worry about? Or how mad is that homeless man in the neighborhood? More fundamentally, how dangerous are the mentally ill in general?

These are compelling questions that require basic information before a reasonable response could be proffered. That’s because the relationship between mental illness and violence is a complex one. About 2% of the general population will be convicted of a violent crime over a 5-year period of time. The for individuals who suffer from a mental illness like schizophrenia is about 7-8%. But to put that increased percentage into perspective, one must compare the risk with other non-psychotic conditions. For instance, the risk of a violent conviction for people who abuse alcohol is also about 7%, and for drug abuse is about 18%. Even individuals with an anxiety disorder are at a greater risk than those in the general public, at about 4-5%.

When you reflect on these numbers, it’s important to keep in mind that most people do not commit violent acts, be they mentally ill, alcoholics, drug users, or those individuals grappling with anxiety.

So how does one identify a mentally disordered individual who might be a danger? Below are some signs and symptoms.

A psychotically paranoid person is potentially dangerous. Frequently, those suffering with paranoia wear their persecutory delusions on their sleeves: e.g., a furtive glare, a muddled question that reveals a suspiciousness decoupled from reality, abrupt displays of anger, or frightening glare. Generally, the psychotically paranoid are themselves in a state of terror and believe that you are threatening them. That’s why so many paranoid individuals become irrational and aggressive when confronted by police, instead of simply complying with their commands. They believe they must defend themselves.

Psychotic people with command hallucinations are dangerous. These are auditory voices commanding them to act in a specific way. For instance, a schizophrenic defendant repeatedly heard a voice telling him that his father was a demon and to “… stab him in the heart now!” It’s difficult to discern this from observation alone. Sometimes, though, the psychotic individual will be arguing with the commanding voice, thus revealing its presence. Or consider the recent school shooting in the halls of a high school in a Detroit suburb, where Ethan Crumbley shot and killed four students. A teacher found a drawing of a gun by Ethan just before the rampage with the words, “The thoughts won’t stop. Help me.”

Delusions are false beliefs that are relentlessly maintained in spite of incontrovertible evidence. Paranoid delusions are dangerous and are frequently revealed verbally in an incidental fashion. For example, a delusional defendant informed me that my cover had been blown: he knew I was a member of Illuminati and doing their dirty work.

A mentally ill person who abuses illicit drugs or alcohol is at risk of becoming violent. The use of hard drugs like methamphetamines by someone with paranoid symptoms is especially at risk. But then again, methamphetamine abusers without a mental illness are at a greater risk to be violent.

A clinical vignette captures the difficulty in discerning when a mentally disordered person’s behavior is disturbing and intrusive, but not potentially lethal. An attorney asked me to evaluate Jason, who was charged with battery and resisting a police officer. A college student, Jason walked into a classroom, shirtless and in shorts, rambling and laughing out loud. As he exited, he bent down and hugged a female student, placing his arms around her neck. She gasped in fear as other students began yelling at him. Jason walked out and was soon arrested by police, but not before disobeying the officers’ commands to stop walking and sit on the curb.

During my evaluation of Jason, he told me that, when he walked into the classroom, he thought he was in a YouTube music video. “I just wanted a hug,” he said. He denied intentionally resisting the officers’ commands, saying, “I wasn’t paying attention… I was in my head…”

Jason had a history of mental illness, with symptoms of auditory hallucinations. He had been diagnosed with schizophrenia, but not with a paranoid form of the illness.

Jason had no history of previous aggression or violence, even when psychotic. He was free of paranoid thinking or command hallucinations. He was not a drug user. Like many who suffer from mental illness, his auditory hallucinations were fairly benign in nature. He would, for example, hear his name being called. When stressed, the voices might call him pejorative names. Still, he had never been violent.

I opined that Jason was at a low risk to become violent. He did not pose an unreasonable risk of danger to the community, especially if he were placed on probation with the requirement that he participate in mental health treatment and that he takes antipsychotic medication.

The court agreed and Jason was placed in a comprehensive treatment program, in lieu of incarceration.

Here’s the takeaways regarding the nexus between mental illness and violence:

Someone with a mental illness who is paranoid and with command hallucinations is potentially dangerous. That risk of violence becomes combustible when substance abuse is mixed with paranoid thinking.

Those displaying these kinds of dangerous symptoms or behavior should be cleared by a mental health professional before returning to their everyday lives.

Individuals with a non-paranoid form of mental illness are not likely to be dangerous. Strange behavior by those with limited social skills does not portend, ipso facto, a risk of violence. Even Jason’s behavior, which was understandably interpreted as dangerous (attempting to hug a stranger), was intrusive and inappropriate, but he was not about to become violent. In actuality, most mentally disordered people are themselves at risk to become victims of violence.


Appelbaum, P. S. (2013). Public safety, mental disorders, and guns. JAMA psychiatry, 70(6), 565-566.

Whiting, D., Lichtenstein, P., & Fazel, S. (2021). Violence and mental disorders: a structured review of associations by individual diagnoses, risk factors, and risk assessment. The Lancet Psychiatry, 8(2), 150-161. (See pp.153 in particular.)

Scott CL and Resnick PJ: Clinical assessment of aggression and violence. In Principles and Practice of Forensic Psychiatry, Third Edition (Editors: Rosner R and Scott CL); CRC Press, Taylor & Francis Group, New York, 2017, pp 623-632.

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